Bidirectional rectifier and phase detector



NV- 10, 1953 H. c. LEHDE 2,658,996

BIDIRECTIONAL RECTIEIER AND PHASE DETECTOR Filed sept. 2L 1949 TTQEYEK Patented Nov. 10, 1953 BIDIRECTIONAL RECTIFIER AND PHASE DETECTOR Henry C. Lehde, Brooklyn, N. Y., assignor to Control Instrument Company, Inc., New York, N. Y., a corporation of New York Application September 27, 1949, Serial No. 118,135

- This invention relates to an improved phase detector and bi-directionalrectiler meansfor producing a uni-directional voltage whose magnitude and polarity is uniquely determined by the magnitude and phase, as referred to some reference phase,` of an alternating voltage.

Ordinarily, such means comprisevariously related ampliiiers and rectifiers, controlled .and biased by a reference Voltage, and appliedin such a mannerthat the outputvoltage will be determined in polarity by the phase of the input voltage relative to the referencevoltage, and be determined in magnitude by the magnitude of the input voltage` All of these applications, however, require that means be provided for adjustment so that, in the absence of input, the output shall bezero; further, these applications which require adjustment means are usually circuits in which the zero output condition for zero inputv voltage is not a stable one, and changesr take place with the aging of the elements comprising these circuits, so that continual adjustment is necessary;`

and further still, these devices are usually critical as to ,the` magnitude of the biasing ,voltagezemployed andthe output like as not is a function 'i of the magnitude ofthe bias voltage as Wellr as of the input voltage.`

An object of this invention is, therefore, to. produce an improved directional rectifier whose,

input is an alternating voltage and Whose output is a uni-directional voltage which is a function of, andY only of, the magnitudeand phase of the alternating input voltage, andV which isunaifected by aging of components or magnitude of bias voltages, andffurther, whose output voltage shall be andremain zero whenever the input voltage (not shown), By'mea'ns of thev crank 5 and the shaft 6," whose'extension carries the dial l, the rotor 8 of the'synchroV is rotatable within the iield of the stator so that the phase of the volt-1 ageer induced in the rotor is variable in a range of360 about somevchosen reference,

be indicated bylzero-on the dial 'I.

z claims; (c1. 25o-27) This voltage, by means of the leads 9 and I0, is introduced into the primary II of transformer I2, which transformer is provided with two center tap secondaries; secondary I3, whose polarity with respect to the primary is additive, and secondary Il whose polarity with respect to primary IIis subtractive. Thus, the voltage erbetween the leadsrl4 and I5 is in phase with the voltage in the primary I I and the voltage e2 between the leads I8 and I9 is 180 out of phase therewith. This is indicated by e1 and er .being i while e2 is 1. Voltage e1` isv applied to two grids 23 and 24 of` the electrondischarge tube 25 which tube contains two complete electron discharge devices 25A and'25B shown as triodes but which may have any other grid controlled configuration. The cathodes 2l and 22 of the electron discharge devices 25A and 25B are connected by means of lead 'Il and returned to the center tap I6 of secondary I3. Thus the grids are alternately negative and-positive with respect to the common cathode and operate 180 apart in phase.

In a similar manner, e2 is applied to the grids 28 and 29 of the electron discharge tube 30Which tube is similar to the'electron discharge tube 25 and comprises the separate elements 36A and 30B. The cathodes 26 and 21 of these devices are connected together by means of lead 'I2 and are returned to the center tap 20 of secondary I'I; thus, these grids also are alternately negative and positive with respect to their common cathodes,Y operatev180 apart-and as regards sections A to, so thatthe current that the grids may draw is limited by the resistance in series which they provide. L .y t t The unknown voltage E is applied lto vtransformer 3t5-across terminals 31 and 33 of Vits .pri-1 maryf.. Thiss-voltage is then amplied in, a

conventional, class A, push-pull-amplifer in order to4 obtain a vo1tage'E"-` which is balanced with respect to groundand proportional. to theY input. Thesecondary 39 oflmtransformer 35 is center tapped Yand 'two yvoltages differingin phase by u 180, one lof which is phase Ywith the drivingl i voltage E, are thus obtained; one voltage between terminalgydu and thecenter tap 42 ofY winding 39 and the other between terminal 4I and center'. tap 42 ofthe same winding. Thesevoltages are" applied, through the resistances 54 and, 55, ,lto the grids 44 and 45 of the dual electron discharge be a linear function oi E. Since E is presentflo across the primary 50 of transiormeri .a simi*-LIF lar voltage is present across the" secondariesTiti? and 58 thereof so that each will deliver voltages across the leads 51 and 68 aswelias-across leads 69 and 10. These voltages are applied by wayiof:

said leads to the anodes, 59, Si, 62 and S3 of the'v electron discharge tubes andati. Y

If the voltages E and er are in phase and the transformer polarities are such that duringth'e. half cycle, when the terminal 31 is positive, the plate59 of tube 25A and plate 62 oftube 30A are positive, grid 23 ofvtube 25A 'and grid29.v oftube B will be positive as well, and the remaining tube elements will be negative. Since only that tube withboth' a positive grid and-platefcan con.` duct," only tubevZA' .will `permit currenttoflow; Oni-the remaining half cycle anodes 59"and,62:'are negative'and' anodesfil and B3 are:positive;1and grids24'and 28 are simultaneously positive while gridsV 23-and zfarenegative; Tube 25B-will thus be conductive; being Vthe only tube having both grid and anode positive.`V Therefore; :whenzthe' unknown voltage and.' the* reference voltage are in :phasei tube 25 'will conduct' either by way of section .Aor section B and;sincefitscathodes 2| an'd122 are-joined by.' way of lead. 'Hand are `inl seriesxwithf resistor '653 to le`ad...'|'.3, lead. 13 will` be positive. and lead 14,1which is connected to the center ltop 60 of. secondary 51 iwhichsupplies the anodes, will be negative.

Ifv the voltage E were. l80"out.0f' phase with the reference voltage' er, vthen theanode 5S and 62 would be negative and th'eanodesh'l:andu63 would'be positive when the grids 23''and 29` were positive and the grids 247 and-2`8l were negative.y ByY the same reasoning, tube 30B will conduct and upon the reversal of the currentsduring the remainder of the cyclev it may Ybe readily shownthat tube 30A will conduct-so that' the cathodes When the phase of E and er differ by 90 or 270 each tube will conduct for one quarter of a cycle and the leads 13 and 14 will each be alternately positive and negative for an equal amount of time. The entire output will, therefore, be an alternating voltage without any direct componentfatfall. To avoid an alternating output, the low pass-lter 15 of ordinary design is provided to absorb all frequencies above a given minimum frequency, and if its cut-orf frequency is less than -that-of. thevoltages applied as E or er the alternating component put out by the rectiners willbe completely absorbed and the potential difference: between-:theterminals 16 and 11 will be proportionall-tof that component of the voltage Efwhich'isnotinquadrature with the reference voltage, in thiscase, -zero.

Since the output will be a maximum for that conditionin which E and er are exactly in phase or in phase opposition, the phase of an unknown Voltage. may be readily determined-by: connecting the same-toterminals 31i andi'fandr'therr rotat-i ing the rotorsB of the'synchro4 i by meansfofcits crank 5 to thatpoint at which thevo1tage-betweenthe terminals .16 yand. 11 isa maximum and` the polarity is such'. .that iterminal16ris positive; with'. respect to terminalll: i. .This makesivoltge er in phase with the unknown 'voltageLEand the' displacementA of the .synchrorotorfin degrees ."as indicated by the dial -1, is.the-phasefdisplacement of the unknown with. respect. to.Y the` 1 reference; Greater` accuracy is obtainable. determining that position of .the dial 1 which indicates-zero output rather than maximum .'output,V since-the' null is much sharper-'.thanthe maximum; atI this point the dial will indicateia .voltagevQO-'i leading or lagging the unknown voltageland by. determine ing the directionV of irotation'from'this dial'r-set-il ting which .would lead tto' a ``maximum' Wemay then determine whether to. add or subtractfrom the'dial setting to'determine th'e phaseof'th'e' un known vo'ltage'exa'ctly. However, inusin'g this method caremust be' taken todetermine whether the null settingis an indication'for the reference' voltage' conditionV which Iis 90'faheadof' or be'-A U hind that of theunknown voltage;V Rsetting-the 2B and 21 ofy tube 30 which are tied together by 5 means of leads'12v` and in series withresistor 6d to lead 14 will be positive and lead 13 which is connected to the center tap 64 of secondary 58 which supplies the anodes oftube'30will'be negative; Y

It is thus evident thatfor a 180 reversal 'in phase of the unknown Voltage E-With respect to the reference voltage er the polarities of leads 13 and 14 will interchange and, since kbothrtubes 25' and 30 are acting as rectiers, their voltage outputs will be proportional to the voltage applied to their plates.

For that condition inwhich the' lvoltages are"v not precisely in phase Yor in phase". opposition,

both tubes 25 and 30 willconduct, eachduring a portion of each cycle; but, sinceithe gridswill be Vpositive for only a portion of the time during which the plates are positive as well. andA since these times are vdetermined entirely by the phase-` of the plate voltages with respect to the' grid voltages, vlead 13 will be more'positive than lead 14, or vice versa, depending upon the phase see. quence and, in addition,..there will'be an alterhating output of twice the frequency ofthe uns Vknown or'reference voltage.

rotor of the motor I so that the"v:lialisagainv at' zero will reduce the voltage output, and possibly reverse the' polarity if the displacement exceeds and yields an output indicating the magnitude 'of the in phase componente? the unknown voltage'andits phase sequen'cewithrespect to' the reference voltage.

Thus a means has beeni'discl'osed through `the* use of which the phase of an unknownvoltage'-y may be actually determined asreferred' to someA reference voltage and whose output isa -linear function of the input. The foregoing description, however, lis intended to describe rather than to' iimii and define the inventive idea herein con-A tained, reference being'madel to the appended claims for that'purpose.: Y, s s

What'is claimed is:

1. A phase'comparator havingareferencelale; ternating current voltage .inputr'an'unknown alternating current voltage input, .andangoutput circuit; a pair of electron discharge..unitseach of said units consisting oftstwo anodes, twogriols;

and a common cathode;.energizing meansfcon V necting .said reference. inputto said grids; fen-"f ergizing. means connecting.. said .anodes-. to saidA unknown input; center tapped means. connecting said grid energizingmeans to said commoncathi-s` ode of each respective electron vdischarge 'uniti further center tapped means interconnecting'. saidi anodes of one discharge unit with the cathodes of the other discharge unit and said output circuit; and further center tapped means interconneeting said anodes of said other discharge unit with the cathodes of said one discharge unit and said output circuit.

2. A phase comparator comprising in combination: first and second electron discharge units each having two anodes, tWo grids, and a common cathode; means applying to said units a reference Voltage and an unknown voltage to .be compared in phase; an output circuit; center tapped means connecting the anodes of said first discharge unit and the cathodes of said second discharge unit to said output circuit; center tapped means connecting the anodes of said second discharge unit and the cathodes of said first discharge unit to said output circuit; means applying opposite poiarities of said reference voltage to the respective grids in each discharge unit; center tapped means connecting said cathodes of said units to said applying means; and means applying opposite polarities of said unknown voltage to the respective anodes in each discharge unit.

HENRY C. LEI-IDE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,936,414 Stone Nov. 21, 1933 2,018,268 Knowles Oct. 22, 1935 2,118,770 Sivertsen May 24, 1938 2,281,995 Purington May 5, 1942 2,429,636 McCoy Oct. 28, 1947 

